Outline

Objective: The globus pallidus internus (GPi) has been established as the target of choice for deep brain stimulation (DBS) in patients with primary forms of dystonia. For myoclonus-dystonia, the GPi is also the most frequently chosen target. In earlier studies, the nucleus ventralis intermedius thalami (Vim) was used to treat the disabling myoclonic jerks in particular. We applied a bifocal (pallidal and thalamic) paradigm stimulation to assess the optimal target in a patient with myoclonus-dystonia.

Methods: A 34-year-old woman had been suffering from myoclonic jerks involving the head and the upper extremities for four years. She also presented with cervical dystonia and dystonic movements of both arms. Botulinum toxin injections did not show beneficial effects. Therefore, she was scheduled to undergo bilateral bifocal CT-stereotactic implantation of quadripolar DBS electrodes (3387, Medtronic) into the GPi and the Vim. The preoperative BFM motor and disability scores were 15 and 7, respectively.

Results: There were no surgically related complications. Postoperatively, extensive testing for alternative stimulation via the four externalized electrodes was performed. While on thalamic stimulation, the patient experienced clearly more pronounced effect for the myoclonic symptoms than with GPi stimulation. Therefore, thalamic stimulation was switched on for chronic stimulation. Follow-up showed an improvement in the BFM motor score by 60% at 24 months. In addition, the myoclonic jerks were completely abated.

Conclusions: Although the GPi has been addressed as the target of choice for dystonia, thalamic Vim should not be completely disregarded under certain circumstances. It may provide a more pronounced effect in patients with refractory myoclonus-dystonia.